Based on the theory of Bio-saturated porous media， the tapered pile was simplified into an Euler beam， and a tapered pile-soil coupling model under the horizontal steady-state vibration was established. Firstly， the potential function is introduced to solve the vibration control equation of soil around each pile section under the plane strain model. The earth pressure around the pile section of each layer is obtained by using variable separation methods and operator decomposition methods. Combining the conditions of pile-soil coupling and displacement continuity， the impedance solution of tapered pile top is obtained. The effects of wedge angle， length diameter ratio， and soil permeability on the top impedance of a wedge-shaped pile are studied based on the analysis of examples. The results show that： 1）in the low-frequency range， the impedance of the tapered pile decreases with the increase of wedge angle； 2）increasing the length of the tapered pile can improve the horizontal impedance and rocking impedance of the pile head； 3） keeping the volume and length of pile unchanged， the horizontal dynamic stiffness decreases with the increase of wedge angle in low-frequency stage， but the result is opposite in high-frequency stage； 4） the existence of liquid phase in soil has a significant effect on the dynamic impedance of pile top， and neglecting the action of the liquid phase in the soil leads to underestimating the dynamic impedance of tapered pile；5） surface soft soil reduces the dynamic impendence of the tapered pile.